1. Field of the Invention
The invention relates to wireless digital communication systems with antenna diversity using OFDM (standing for Orthogonal Frequency Division Multiplex) type modulation. The antenna diversity helps to improve the quality of the transmission link in terms of reliability and robustness. Such communication systems are used for example in local wireless networks of the IEEE 802.11a or Hiperlan2 type which use burst transmission.
2. Description of the Prior Art
To find out more about transmissions using modulation of OFDM type, the person skilled in the art can consult: Allard M. et LASSALLE R., “Principes de modulation et de codage canal en radiodiffusion numérique vers des mobiles.” [Principles of modulation and channel coding in digital radio broadcasting to mobiles], UER-Technique journal, No. 224, Aug. 1987, pp. 168-190; M.C.D. Maddocks, “An introduction to digital modulation and OFDM techniques”, BBC Research and Development Report, BBC RD 1993/10; Le Floch B., Alard M. and Berrou C., “Coded Orthogonal Frequency Division Multiplex”, Proceedings of the IEEE, vol. 83, No. 6, Jun. 1995, pp. 982-996. More particularly, the invention pertains to a process for selecting an antenna from several antennas available at the input of an OFDM radio signals receiver with antenna diversity, with a view to favouring the transmission channel delivering a signal leading to the lowest binary error rate after decoding.
To calculate the binary error rate on a transmission channel, one generally makes use of a certain number of bits of the preamble of each frame dispatched in the radio signal which is transmitted by the channel. However, this calculation is expensive in terms of time because it is necessary to decode a large number of bits and it is not suited to an antenna diversity receiver having to undergo temporally frequent changes of reception antenna.